a. Field of the Invention
The present disclosure relates to catheter devices and systems, including devices and methods for determining angle or degree of bend/deflection, as well as the location and orientation of a catheter and/or sheath within a treatment area.
b. Background Art
Electrophysiology (EP) catheters are used in connection with an ever-increasing number of procedures. Such catheters have been used, for example, for diagnostic, therapeutic, mapping, and ablative procedures. Catheters are commonly manipulated through a patient's vasculature to an intended site, for example a site within the patient's heart, and may carry one or more electrodes that may be used for mapping, ablation, diagnosis, or other treatments.
Traditional techniques for manipulating catheters to, and within, a treatment area generally require a user to manipulate a handle connected to a catheter. The handle commonly includes a mechanism connected to steering wires that controls the deflection of the associated catheter. A second handle is often provided for controlling deflection of an associated sheath. Rotating and advancing a catheter or sheath generally requires an electrophysiologist to physically rotate and advance the associated handle. Alternatively, a robotic system may be employed to manipulate the pull wires and control distal deflection. With either method, knowledge of the distal bending characteristics and position of the catheter is commonly utilized.
To determine position and bending characteristics, a feed-back system may be used to provide the location of the catheter. Feedback systems typically externally monitor the catheter's position in three dimensional space, and provide information concerning the associated movement of a catheter to a user. Exemplary feedback systems include the EnSite NavX™ impedance-based system commercialized by St. Jude Medical, Inc., as well as the magnetically-based Medical Positioning System (gMPS) for navigation developed by St. Jude Medical, Inc. through its MediGuide Inc. business unit of Haifa, Israel. Some feedback systems may, however, simply be reactionary, in that they may simply determine the direction and magnitude of a movement after the movement has been made.
The three-dimensional location and distal bending characteristics of a catheter may be predicted if the displacement status of the steering wires is known. In particular, deflection characteristics are affected by the length of steering wires extending beyond a fulcrum (i.e., the location or point at which deflection begins). By knowing the respective distal steering wire lengths, along with the current catheter position, a new position can be expressed in terms of a steering wire movement. Conventional prediction methods generally monitor steering-wire length at the proximal end of the catheter with the assumption that the proximal steering wire movement is directly related to the distal steering wire movement. In practice, however, the steering wires extending to the distal end of the catheter may be a meter or more in length, and may be affected by a number of factors, including compression in the catheter body, stretching of pull wires, curvature of the proximal body of the catheter, and other anomalies. Current prediction methods thus may not always provide accurate prediction of distal steering wire lengths.